Yong Zhang

Chemically reduced graphene (CR-G)/poly(ethylene oxide) (PEO) composites are prepared by a simple aqueous mixing method. Graphite oxide (GO) is prepared by a modified Hummers method and further dispersed in water to form graphene oxide (G-O). The as prepared G-O is mixed with PEO and in situ reduced by l-ascorbic acid. CR-G monolayers are ∼1 nm in thickness and ∼1.5 μm in both length and width as confirmed by AFM, indicating their large aspect ratio of about 1500. G-O is dispersed in PEO at the molecular level due to hydrogen bonding, and PEO acts as a barrier for CR-G layers to prevent agglomeration during the process of reduction. CR-G/PEO composites have high permittivity, resulting from the uniform dispersion of electrically conductive CR-G with high aspect ratio. CR-G/PEO composite (2.6 vol %) shows high microwave absorbing capacity as its minimum reflection loss is −38.8 dB. CR-G sheets form a huge number of electrical pathways which can dissipate microwave energy into heat effectively as well as dielectric relaxation and interface scattering induced by large CR-G/PEO interfaces.

Abstract Biodegradable polymer blends consisting of poly( L ‐lactic acid) (PLLA) and poly(butylene succinate) (PBS) were prepared in the presence of dicumyl peroxide (DCP). The effects of DCP content on the mechanical properties, thermal and rheological behavior, phase morphology as well as the toughening mechanism of the blends were investigated. The notched Izod impact strength of PLLA/PBS (80/20) blend significantly increased after the addition of 0.05–0.2 phr DCP, but the strength and modulus monotonically decreased with increasing DCP content. PBS acted as a nucleating agent at the environmental temperature below its melting temperature and accelerated the crystallization rate of PLLA but had little effect on its final degree of crystallinity. The degree of crystallinity of PBS and the cold crystallization ability of PLLA gradually reduced with increasing DCP content. The addition of DCP induced an increase in viscosity of the blends at low frequencies as well as finer dispersion of PBS particles and better interfacial adhesion between PLLA and PBS, indicating the in situ compatibilization occurred between the two components. The optical clarity of PLLA/PBS blends was significantly improved after the addition of DCP, which was in accordance with the crystallization behavior and phase structure of the blends. POLYM. ENG. SCI., 2009. © 2008 Society of Plastics Engineers